Forward declare typedef within C++ class

Question

What\'s the best solution to forward declare a typedef within a class. Here\'s an example of what I need to solve:

class A;
class B;

class A
{
    typedef boos         


        

Answer 1

There is no such thing as forward declaring a typedef unfortunately. However, there's a trick using late template instantiation:

template  class BImpl;

template 
class AImpl
{
public:
    typedef boost::shared_ptr Ptr;
    typename BImpl::Ptr foo();
};

template 
class BImpl
{
public:
    typedef boost::shared_ptr Ptr;
    typename AImpl::Ptr bar();
};

typedef AImpl A;
typedef BImpl B;

This should hopefully accomplish the thing you're aiming for.